Year	Percent of Total
1960-01-01	56.6640469243801
1961-01-01	56.3028635709137
1962-01-01	56.2875983252064
1963-01-01	56.4903507092392
1964-01-01	56.7785188857445
1965-01-01	57.1306194262144
1966-01-01	57.1586346281894
1967-01-01	57.4724241803734
1968-01-01	58.0038935198788
1969-01-01	58.6467043441302
1970-01-01	59.3300426117293
1971-01-01	60.1496662247142
1972-01-01	60.8438511051664
1973-01-01	61.5127317738222
1974-01-01	62.2936264343712
1975-01-01	63.2190447502149
1976-01-01	64.1549611793668
1977-01-01	65.3092561472188
1978-01-01	66.5128556230208
1979-01-01	67.5522829963335
1980-01-01	68.3431096170516
1981-01-01	68.7487551010977
1982-01-01	68.9649717722066
1983-01-01	69.0419899103226
1984-01-01	69.0883751942932
1985-01-01	69.1631779095635
1986-01-01	69.4428462478779
1987-01-01	69.7309474350554
1988-01-01	70.0010392729296
1989-01-01	70.2291242961099
1990-01-01	70.4205115006437
1991-01-01	70.6712984157396
1992-01-01	70.8521243007395
1993-01-01	70.9978766093605
1994-01-01	71.1539192011476
1995-01-01	71.3348852079143
1996-01-01	71.4064990763897
1997-01-01	71.5962790668406
1998-01-01	71.8107162430435
1999-01-01	71.9835235283067
2000-01-01	72.1244230267658
2001-01-01	72.4060761292330
2002-01-01	72.6324215832228
2003-01-01	72.8438080485999
2004-01-01	73.0937170024918
2005-01-01	73.3972967126412
2006-01-01	73.8479348653776
2007-01-01	74.2892587944707
2008-01-01	74.6884691101553
2009-01-01	74.9755988310351
2010-01-01	75.0919152578972
2011-01-01	75.0787842591407
2012-01-01	74.9587238206017
2013-01-01	74.6920608328574
2014-01-01	74.2413403010023
2015-01-01	73.6033959999178
2016-01-01	73.0221230279769
2017-01-01	72.2082754064118